Unexpected token ' in JSON at position 0

[kush-13]

unmodified code of the repo gives error when i make the following put request :
curl -X PUT http://localhost:3001/api/v1/clients/1 -H "Content-Type: application/json" -d '{"status":"in-progress", "priority": 6}'
error :
SyntaxError: Unexpected token ' in JSON at position 0 at JSON.parse (<anonymous>) at createStrictSyntaxError (D:\web\shiptivitas-2\node_modules\body-parser\lib\types\json.js:158:10) at parse (D:\web\shiptivitas-2\node_modules\body-parser\lib\types\json.js:83:15) at D:\web\shiptivitas-2\node_modules\body-parser\lib\read.js:121:18 at invokeCallback (D:\web\shiptivitas-2\node_modules\raw-body\index.js:224:16) at done (D:\web\shiptivitas-2\node_modules\raw-body\index.js:213:7) at IncomingMessage.onEnd (D:\web\shiptivitas-2\node_modules\raw-body\index.js:273:7) at IncomingMessage.emit (events.js:327:22) at endReadableNT (internal/streams/readable.js:1327:12) at processTicksAndRejections (internal/process/task_queues.js:80:21)